We offer two improvements to prior results concerning global stability of the 2D Ricker Equation. We also offer some new methods of approach for the more pathological cases and prove some miscellaneous results including a special nontrivial case in which the mapping is conjugate to the 1D Ricker map along an invariant line and a proof of the non-existence of period-2 points.

Figure 1.
The curves $T^k(C)$ for $k=0,1,2,3$ are shown, as well as the unstable manifolds (thicker lines) from $(p,0)$ and $(0,q)$. The unstable manifolds intersect at the coexistence fixed point. The curves, ordered from bottom left to top right, go $C, T^2(C)$, the unstable manifolds, $T^3(C) $, and then finally $T(C)$

Figure 2.
The figure shows the upper bounds implied by Theorems 2.3, 3.2, and Conjecture 1, respectively. In the left column, we have the upper bounds for $p$ and in the right column we have the upper bounds for $q$. We have capped the upper bounds at 2 for the plots since the fixed point loses stability past $p,q=2$

Figure 4.
In the left figure, we show the isocline $L_p$ and the curve $y=-\frac{1}{a}\ln\left(\frac{2x^*}{x}-1\right)-\frac{x-p}{a}$ by solid lines. The shaded regions are where the function moves closer in the $x$ coordinate. On the right, the isocline $L_q$ and the curve $x=-\frac{1}{b}\ln\left(\frac{2y^*}{y}-1\right)-\frac{y-q}{b}$ are shown as solid lines. The shaded regions are where the $y$ coordinate moves closer. The union of the two regions is the entire plane

Figure 5.
A graph of the function $G(x,y)$ is shown for parameters $p=1.8$, $q=1.9$, $a=0.2$, $b=0.3$. We observe that this appears to be a concave function with a maximum at the fixed point illustrated by the vertical line

Figure 8.
The plane is divided into six regions $H_n$ by the isoclines $L_p$, $L_q$ (in the figure $L_p$ is the solid line from the top middle to the bottom, and $L_q$ is the other solid line) and the line $y=\frac{y^*}{x^*}x$ (shown dashed